1. Field of the Invention
The present invention relates to a digital camera and an image signal generating method, in particular, a digital camera with a video output terminal for externally outputting a composite video signal having a set of a horizontal blanking period and a video period for each scanning line, and an image signal generating method of the digital camera.
2. Description of the Related Art
In recent years, the digital camera has become remarkably widespread and exceeds the film camera in annual shipments.
In the conventional digital camera, the aspect ratio of an image taken by an imaging element such as CCD and CMOS image sensor (object image) is generally set as 4:3. This corresponds with the aspect ratio of a conventional television receiver or a display region of a display device, such as liquid crystal display mounted on the digital camera as a monitor for the object image is 4:3.
On the other hand, television sets having the aspect ratio of the display region of 16:9 (so-called wide size) (hereinafter referred to as “wide TV”) has gained in popularity recently and it is forecasted that the display device mounted on digital cameras with a display region of wide size will become widely used.
In this case, when the object image photographed by the digital camera using the imaging device with the aspect ratio of the photographed image of 4:3 is displayed on an external wide TV or the display device of wide size mounted as the monitor for the object image, blank region(s) are generated in part(s) of the display region, since the aspect ratio remains 4:3.
Thus, the display of various additional information, such as photographing conditions of the displayed object image, various icons and thumbnail images can be considered.
When a large image having an aspect ratio of 4:3 and small image(s) (corresponding to the above-mentioned additional information) are displayed in the display region having the aspect ratio of 16:9, the display position of each image in the horizontal direction is fixed. This may cause obstacles to the appreciation of each image depending on the installation position conditions of the image display device and so on. To prevent such obstacle(s), there is an art where the big image and the small image(s) can be optionally switched between display on the right side and the left side of the display region by the user's operation (refer to Japanese Patent No. 3097138, for example).
To provide a television set capable of properly displaying characters on a screen having a different aspect ratio when the image signal is displayed on the screen, according another related art, the display position of the characters (corresponding to the above-mentioned additional information) is changed in response to the display mode so that the characters are superimposed and displayed within the scope of the displayed image (refer to Japanese Patent No. 2998156, for example).
The conventional digital camera often has a video output terminal for outputting a composite video signal so that a photographed object image can be displayed on a television set.
To simultaneously display the object image and the additional information on a display device as a monitor for the object image mounted on a digital camera, since image signals and composite video signals supplied to the display device are greatly different from each other in specification, a digital camera of this kind requires separate image signal generating circuits systems by signal, thereby causing the problem of complicating configuration.
Since the technologies described in Japanese Patent No. 3097138 and Japanese Patent No. 2998156 fail to consider the provision of a video output terminal, these arts cannot overcome this problem.